Pillared Clays and Pillared Layered Solids

1999 ◽  
Vol 71 (12) ◽  
pp. 2367-2371 ◽  
Author(s):  
R. A. Schoonheydt ◽  
T. Pinnavaia ◽  
Gerhard Lagaly ◽  
Nick Gangas
Keyword(s):  
Classification Scheme ◽  
Pillared Clays ◽  
Inorganic Compound ◽  
Layered Compound ◽  
Systematic Classification ◽  
Characterization Methods ◽  
Interlayer Region ◽  
Layered Solid

Pillaring is a commonly used procedure to transform a layered crystalline inorganic compound into a material with microporosity and mesoporosity. First, the terms "layered compound, pillaring, pillaring agent and interlayer region" are defined, and then the term pillared layered solid or pillared compound. In the second part, the standard characterization methods and procedures and a systematic classification scheme are proposed.

scholarly journals Study of the textural properties of some layered double hydroxides

2013 ◽  
Vol 21 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Cornelia-Magda Puscasu ◽  
Carmen Gherasim ◽  
Dragos Mardare ◽  
Gabriela Carja
Keyword(s):  
Layered Double Hydroxides ◽  
Structural Characteristics ◽  
Chemical Species ◽  
Textural Properties ◽  
Layered Compounds ◽  
Layered Compound ◽  
X Ray Diffraction ◽  
Anionic Clays ◽  
Interlayer Region ◽  
Double Hydroxides

Abstract Layered double hydroxides (LDHs) are one of the nano ordered layered compounds. The importance of layered compound is based on their ability to retain chemical species with electrical charges compatible to those of the layers. They may be used in areas such as catalysis, industry, medicine, environmental protection, construction etc. Layered double hydroxides are anionic clays comprising positively charged layers with anions and water molecules intercalated in the interlayer region. The aim of this work was to obtain Cu and/or Ni substituted layered double hydroxides with different micromorphology characteristics. The obtained results pointed out that the relationship between LDHs composition and their textural properties can be controlled. The layered double hydroxides samples were fabricated by using direct coprecipitation method. Field Emission Scanning Electron Microscope (FE-SEM) and X-Ray Diffraction (XRD) analyses were used to study the textural characteristics and the structural characteristics of the samples.

scholarly journals Kinetic regimes and limiting cases of gas uptake and heterogeneous reactions in atmospheric aerosols and clouds: a general classification scheme

2013 ◽  
Vol 13 (1) ◽  
pp. 983-1044
Author(s):  
T. Berkemeier ◽  
A. J. Huisman ◽  
M. Ammann ◽  
M. Shiraiwa ◽  
T. Koop ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Classification Scheme ◽  
Transport Processes ◽  
Heterogeneous Reactions ◽  
Diffusion Reaction ◽  
Systematic Classification ◽  
Gas Uptake ◽  
Reaction Systems

Abstract. Heterogeneous reactions are important to atmospheric chemistry and are therefore an area of intense research. In multiphase systems such as aerosols and clouds, chemical reactions are usually strongly coupled to a complex sequence of mass transport processes and results are often not easy to interpret. Here we present a systematic classification scheme for gas uptake by aerosol or cloud particles which distinguishes two major regimes: a reaction-diffusion regime and a mass-transfer regime. Each of these regimes includes four distinct limiting cases, characterized by a dominant reaction location (surface or bulk) and a single rate-limiting process: chemical reaction, bulk diffusion, gas-phase diffusion or mass accommodation. The conceptual framework enables efficient comparison of different studies and reaction systems, going beyond the scope of previous classification schemes by explicitly resolving interfacial transport processes and surface reactions limited by mass transfer from the gas phase. The use of kinetic multi-layer models instead of resistor model approaches increases the flexibility and enables a broader treatment of the subject, including cases which do not fit into the strict limiting cases typical of most resistor model formulations. The relative importance of different kinetic parameters such as diffusion, reaction rate and accommodation coefficients in this system is evaluated by a quantitative global sensitivity analysis. We outline the characteristic features of each limiting case and discuss the potential relevance of different regimes and limiting cases for various reaction systems. In particular, the classification scheme is applied to three different data sets for the benchmark system of oleic acid reacting with ozone. In light of these results, future directions of research needed to elucidate the multiphase chemical kinetics in this and other reaction systems are discussed.

Pillared Clays and Micas

1987 ◽  
Vol 111 ◽  
Author(s):  
Jack W. Johnson ◽  
John F. Brody
Keyword(s):  
Petroleum Industry ◽  
Pillared Clay ◽  
Pillared Clays ◽  
Liquid Fuels ◽  
Petroleum Processing ◽  
Smectite Clays ◽  
Interlayer Region ◽  
Subsequent Calcination ◽  
Clay Layers ◽  
Potential Use

AbstractThe interest in the petroleum industry in converting heavier feeds to liquid fuels has led to a search for microporous materials with pore sizes larger than those found in the faujasitic zeolites which form the basis of many petroleum processing catalysts. Materials with zeolite-like pores in the 10 Å range can be synthesized by intercalating large polyoxocations between the layers of smectite clays. Subsequent calcination dehydrates the cations and converts them into oxide pillars that prop the clay layers apart, resulting in permanent microporosity in the interlayer region. Pillared clays have been studied extensively during the last decade due to their potential use in petroleum processing as cracking and hydrocracking catalysts. Previous workers have primarily utilized smectite clays such as montmorillonite and hectorite as the starting layered material for pillared clay. We now report that synthetic fluoromicas, clay-like materials of layer charge density higher than that of smectites, can also be pillared with polyoxoaluminum cations to form aluminapillared fluoromicas that are thermally stable up to 700°C.

Classification and Use of Terms for Amplification and Related Reactions

1999 ◽  
Vol 71 (7) ◽  
pp. 1331-1335
Author(s):  
D. T. Burns ◽  
A. Townshend
Keyword(s):  
Classification Scheme ◽  
Systematic Classification

A systematic classification scheme is given for the various types of amplification and related reactions currently available. The report extends and refines earlier IUPAC recommendations (Pure Appl. Chem.54 (1982), 2553-2556) to include non-multiplication reactions.

scholarly journals Kinetic regimes and limiting cases of gas uptake and heterogeneous reactions in atmospheric aerosols and clouds: a general classification scheme

2013 ◽  
Vol 13 (14) ◽  
pp. 6663-6686 ◽  
Author(s):  
T. Berkemeier ◽  
A. J. Huisman ◽  
M. Ammann ◽  
M. Shiraiwa ◽  
T. Koop ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Classification Scheme ◽  
Transport Processes ◽  
Heterogeneous Reactions ◽  
Diffusion Reaction ◽  
Systematic Classification ◽  
Gas Uptake ◽  
Reaction Systems

Abstract. Heterogeneous reactions are important to atmospheric chemistry and are therefore an area of intense research. In multiphase systems such as aerosols and clouds, chemical reactions are usually strongly coupled to a complex sequence of mass transport processes and results are often not easy to interpret. Here we present a systematic classification scheme for gas uptake by aerosol or cloud particles which distinguishes two major regimes: a reaction-diffusion regime and a mass transfer regime. Each of these regimes includes four distinct limiting cases, characterised by a dominant reaction location (surface or bulk) and a single rate-limiting process: chemical reaction, bulk diffusion, gas-phase diffusion or mass accommodation. The conceptual framework enables efficient comparison of different studies and reaction systems, going beyond the scope of previous classification schemes by explicitly resolving interfacial transport processes and surface reactions limited by mass transfer from the gas phase. The use of kinetic multi-layer models instead of resistor model approaches increases the flexibility and enables a broader treatment of the subject, including cases which do not fit into the strict limiting cases typical of most resistor model formulations. The relative importance of different kinetic parameters such as diffusion, reaction rate and accommodation coefficients in this system is evaluated by a quantitative global sensitivity analysis. We outline the characteristic features of each limiting case and discuss the potential relevance of different regimes and limiting cases for various reaction systems. In particular, the classification scheme is applied to three different datasets for the benchmark system of oleic acid reacting with ozone in order to demonstrate utility and highlight potential issues. In light of these results, future directions of research needed to elucidate the multiphase chemical kinetics in this and other reaction systems are discussed.

scholarly journals Nomenclature of structural and compositional characteristics of ordered microporous and mesoporous materials with inorganic hosts(IUPAC Recommendations 2001)

2001 ◽  
Vol 73 (2) ◽  
pp. 381-394 ◽  
Author(s):  
L. B. McCusker ◽  
F. Liebau ◽  
G. Engelhardt
Keyword(s):  
Chemical Composition ◽  
Mesoporous Materials ◽  
Classification Scheme ◽  
Inorganic Materials ◽  
Crystal Chemical ◽  
Chemical Formula ◽  
Crystal Chemical Formula ◽  
Pore System ◽  
Systematic Classification ◽  
Guest Species

A system of terms applicable to ordered microporous and mesoporous materials is proposed, and rules for writing a standardized crystal chemical formula for such materials are presented. The recommendations are based both on common usage and on a systematic classification scheme. The nomenclature has been developed to encompass all inorganic materials with ordered, accessible pores with free diameters of less than 50 nm. The crystal chemical formula describes the chemical composition of both the guest species and the host, the structure of the host, the structure of the pore system, and the symmetry of the material. This formula can be simplified or expanded to suit the user's requirements.

Statistical analysis of classification

1966 ◽  
Vol 24 ◽  
pp. 188-189
Author(s):  
T. J. Deeming
Keyword(s):  
Multivariate Analysis ◽  
Statistical Analysis ◽  
Classification Scheme ◽  
Analytical Procedure ◽  
Narrow Band ◽  
Scientific Research ◽  
Maximum Amount ◽  
Amount Of Information

If we make a set of measurements, such as narrow-band or multicolour photo-electric measurements, which are designed to improve a scheme of classification, and in particular if they are designed to extend the number of dimensions of classification, i.e. the number of classification parameters, then some important problems of analytical procedure arise. First, it is important not to reproduce the errors of the classification scheme which we are trying to improve. Second, when trying to extend the number of dimensions of classification we have little or nothing with which to test the validity of the new parameters.Problems similar to these have occurred in other areas of scientific research (notably psychology and education) and the branch of Statistics called Multivariate Analysis has been developed to deal with them. The techniques of this subject are largely unknown to astronomers, but, if carefully applied, they should at the very least ensure that the astronomer gets the maximum amount of information out of his data and does not waste his time looking for information which is not there. More optimistically, these techniques are potentially capable of indicating the number of classification parameters necessary and giving specific formulas for computing them, as well as pinpointing those particular measurements which are most crucial for determining the classification parameters.

Introductory paper

1966 ◽  
Vol 24 ◽  
pp. 3-5
Author(s):  
W. W. Morgan
Keyword(s):  
Line Intensity ◽  
Classification Scheme ◽  
Two Dimensional ◽  
Spectral Classification ◽  
Dimensional Array ◽  
Rr Lyrae ◽  
Metallic Line ◽  
Introductory Paper ◽  
Parameter Varying ◽  
Definition Of

1. The definition of “normal” stars in spectral classification changes with time; at the time of the publication of theYerkes Spectral Atlasthe term “normal” was applied to stars whose spectra could be fitted smoothly into a two-dimensional array. Thus, at that time, weak-lined spectra (RR Lyrae and HD 140283) would have been considered peculiar. At the present time we would tend to classify such spectra as “normal”—in a more complicated classification scheme which would have a parameter varying with metallic-line intensity within a specific spectral subdivision.

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